The present invention relates to optical elements having variable optical properties such as variable-focus lenses, variable-focus diffraction optical elements, variable deflection angle prisms and variable-focus mirrors, and an optical system including such optical elements. The present invention is also concerned with the application of that optical system to optical finders of cameras, digital cameras and TV cameras; viewing optical systems such as telescopes, microscopes and binoculars; spectacles; video projectors; cameras; digital cameras; TV cameras; and endoscopes.
Referring to conventional lenses formed of polished glass materials or molded lenses, their focal lengths cannot be varied because they cannot transform by themselves. For this reason, mechanical structures become complicated, which are used to move the lenses or lens groups comprising the same along the axial direction for focusing and zooming purposes.
Since motors, etc. are used to mechanically move some of the lens groups, they offer problems such as increased power consumptions, noisy sounds, slow responses, and time-consuming movement of lens groups.